Polymers having terminal amino groups and use thereof as additives for zinc and zinc alloy electrodeposition baths
View Patent ↗Additives for electrolyte baths for the electrodeposition of zinc or zinc alloy layer are described. The additives are polymers with terminal amino groups. These polymers are obtainable by reaction of at least one diamino compound (having two tertiary amino groups) with at least one di(pseudo)halogen compound, wherein the diamino compound is used in stoichiometric excess. The additives effect, in particular, a very little formation of bubbles and only few burnings as well as a uniform distribution of layer thickness in the electrodeposition of zinc or zinc alloy layers.
1. Electrolyte bath for electrodeposition of a zinc or zinc alloy layer, wherein the electrolyte bath contains (i) zinc cations and optionally additional metal ions and (ii) a polymer of the following formula I
A-[-L-A-] n -L-A (I)
wherein A represents a unit derived from a diamino compound of one of the following formulae II to VII
wherein
X and Y each can be the same or different and represent O or NR, wherein R stands for H or C 1 -C 6 -alkyl,
Z each may be the same or different and represents O or S,
R1, R2, R5, and R6 each may be the same or different and represent a substituted or unsubstituted hydrocarbon residue with 1 to 10 carbon atoms, and
R3, R4, R8 each may be the same or different and represent (CH 2 ) p , wherein p stands for an integer of 2 to 12 or for a [CH 2 CH 2 O] m —CH 2 CH 2 — group, wherein m is between 1 and 40,
wherein L stands for a divalent residue, which is selected from the group consisting of
—(CH 2 ) q —, wherein g is between 1 and 12;
—CH 2 —CH(OH)—CH 2 —; and
—[CH 2 CH 2 O] r —CH 2 CH 2 —, wherein r is between 1 and 40;
wherein the single units A may be the same or different,
wherein the single units L may be the same or different,
wherein n represents an integer and n>0, and
wherein the polymer chain has units A at both ends.
2. Electrolyte bath according to claim 1 , wherein R1, R2, R5, and R6 each may be the same or different and represent methyl, ethyl, hydroxyethyl or —CH 2 CH 2 (OCH 2 CH 2 ) y —OH, wherein y is between 0 and 4.
3. Electrolyte bath according to claim 1 , wherein R3 and R4 may each be the same or different and represent an ethylene, propylene, —(CH 2 ) 2 —O—(CH 2 ) 2 — or —(CH 2 ) 2 —O—(CH 2 ) 2 —O—(CH 2 ) 2 — group.
4. Electrolyte bath according to claim 1 , wherein L represents a divalent residue, which is selected from the group consisting of —(CH 2 ) q —, wherein q is between 2 and 4, —(CH 2 ) 2 —O—(CH 2 ) 2 — and —(CH 2 ) 2 —O—(CH 2 ) 2 —O—(CH 2 ) 2 —.
5. Electrolyte bath according to claim 1 , wherein the polymer is obtained by reacting one or more diamino compounds of formulae II to VII with one or more compounds of the following formula VIII,
P-L-Q (VIII)
wherein L has the same meaning as in formula I and wherein P and Q each may be the same or different and represent halogens or pseudohalogens, and
wherein the ratio (n A :n B ) of the total amount of substance used of the compound(s) of formulae II to VII (n A ) to the total amount of substance of the compound(s) of formula VIII (n B ) is at least 1.1:1.
6. Electrolyte bath according to claim 5 , wherein the ratio n A :n B is at least 1.3:1.
7. Electrolyte bath according to claim 5 , wherein the halogens are selected from the group consisting of Cl, Br and I.
8. Electrolyte bath according to claim 5 , wherein the pseudohalogens are selected from the group consisting of mesylate (OMs), triflate (OTf), nonaflate (ONf), and tosylate (OTs).
9. Electrolyte bath according to claim 1 , wherein the polymer of formula I does not have organically bound halogen.
10. Electrolyte bath according to claim 1 , wherein the polymer of formula I has a molecular weight of at least 500 g/mol.
11. Electrolyte bath according to claim 1 , wherein the polymer of formula I is contained in an amount of 0.01 to 50 g/L.
12. Electrolyte bath according to claim 1 , wherein halide ions have been added to the polymer of formula I.
13. Electrolyte bath according to claim 12 , wherein the addition of halide ions has been carried out by addition of the corresponding mineral acids, by quaternization of a determinal tertiary amino group with the corresponding alkyl halides or by addition of alkaline, earth alkaline, zinc or ammonium halides.
14. Electrolyte bath according to claim 12 , wherein the polymer of formula I has been acidified with about 2 equivalents of hydrochloric acid per equivalent of polymer.
15. Process for electrodeposition of glossy and planar zinc or zinc alloy coatings, wherein a substrate to be coated is immersed in the electrolyte bath according to claim 1 and a zinc or zinc alloy coating is deposited on the substrate by electroplating in the electrolyte bath.